Malaria epidemiology in the south-western forest area of Cote d'Ivoire (Region of Tai)

An epidemiological study on malaria was undertaken between July 7 995 and July 7996 in two villages (Zaipobly and Gahably) and their encampments (Kouassikro, Hamanikro and Konankro), in the south-western forest area of Cote d'Ivoire (region of Tai). The parasitological scheme comprised a total of 2023 tests performed on children aged from 0 to 74 years. The species found were Plasmodium falciparum, R malariae and P. ovale with a proportion of 84%, 74% and 2% respectively. The global parasite prevalence of all Plasmodium species was 85% and malaria was holoendemic. The average parasitic density decreased progressively as the age increased, in contrast to the plasmodic index which did not vary. All the malarial indexes were similar in the villages and their encampments. Only overall fever prevalence was permanent and in all age groups it was higher in the encampments than in the villages. The entomological findings showed that transmission was permanent and intense throughout the year with a recrudescence during the rainy season. Transmission was attributed to Anopheles gambiae s.l. in 85% of the cases whereas An. funestus played a secondary role. The average sporozoitic index was 7.6% and varied between 1.1% and 16.7%. The entomological inoculation rate was of 400 infected bites per person-year for An. gambiae s.l. In such conditions of intense transmission, acquisition of premunition starts at a very early age. This assertion is verified by the average parasite density and the frequency of high parasitic densities which were at their maximum between I and 4 years of age and decreased thereafter as the age increased. The paludometric and entomologic indexes obtained are the most elevated ever to have been observed in Cote d'Ivoire, as a result of considerable ecological changes linked to the deterioration of the forest environment over the past 30 years. This deterioration has probably been caused by demographic pressure resulting from internal and foreign immigration to the Tai region and more especially by the influx of Liberian refugees.